Copper base alloys containing reactive elements (Cr, Ti, V, Zr, Mg, B, Be, Sr, Y, Ce, Cb) provide combinations of high strength and high electrical conductivity compared to pure copper or copper containing relatively common alloying elements. A certain problem, however, is presented by the addition of these reactive elements to a copper base. These elements usually possess high melting points which, along with their reactivity, cause problems in the charging of these elements to a molten copper base.
The addition of such reactive elements to copper and copper alloy bases has usually been accomplished by utilizing a copper-reactive element master alloy as the charging system to the molten copper or copper alloy base. This procedure adds to the cost of the final alloy beyond the straight addition of the reactive element since the special processing needed to produce such a master alloy makes such alloys rather expensive and since the amount of reactive element in such a master alloy is usually limited to less than about 10% by weight of the master alloy. This weight restriction generally necessitates the use of relatively large quantities of master alloy to obtain final copper base alloys containing greater than 1% reactive element.
One way of solving this problem would be to utilize pure or nearly pure reactive elements in the charging process of the copper or copper alloy bases. This procedure presents its own problems since the interdiffusion rates of copper and the reactive elements at the molten copper base temperatures are quite slow. An excessively long alloying time is therefore needed to dissolve normal size pieces of these reactive elements (e.g., flakes or pellets).
One way of overcoming this problem has been to provide reactive elements in powder form and directly inject such powder into the molten copper or copper alloy base. While powders provide for shorter interdiffusion rates into the molten base, the large surface area presented by the powders and the inherent reactivity of the elements in powder form present oxidation problems with such a method during charging of the powdered elements to the molten copper or copper alloy base.
One method of overcoming these problems has been to provide such reactive elements in solid clad wire form for charging into a molten copper or copper alloy base. This method is presented in U.S. Pat. No. 3,738,827, which is assigned to the Assignee of the present invention. Such a method alleviates many of the problems discussed above but, in turn, provides the additional step of forming said reactive elements into wire form and then cladding such a wire with a material compatible with the molten base.
It is a principal object of the present invention to provide a method for charging molten copper or copper alloy bases with reactive elements so that the elements readily dissolve with minimal problems from oxidation.
It is a further object of the present invention to provide for charging of reactive elements in powder mixture form to molten copper or copper alloy bases so that the reactive element powders are initially protected by an outer covering which is compatible with the molten bases.
It is an additional object of the present invention to provide for the rapid incorporation of reactive elements into molten copper or copper alloy bases up to the desired weight percentage limits without long melting times or large quantities of master alloys.
Additional objects and advantages will become more apparent from a consideration of the following specification.